[WTF-1907] Fix and improve how-to guide for building pluggable web widgets

[legio-vi-ferrata]

We have previously refactored the Part 1 of the guide for building pluggable web widgets. This PR is a follow-up story to upgrade Part 2 with the latest information and conventions as well. This has become necessary as the first part now uses functional React components in code examples with which following the Part 2 is not possible.

In addition, the PR contains several other improvements for both Part 1 and Part 2.

Note to Reviewer/Tester: I would heavily recommend running the dev server of the repository and following the steps at least once. This would also probably make it easier to see the differences among example code snippets.
Release Information: The PR can be merged and released as soon as possible after its draft status is lifted.

[ConnorLand]

Thanks @legio-vi-ferrata ! Is there a tester you recommend if I have questions or get error codes?

[legio-vi-ferrata]

Thanks @legio-vi-ferrata ! Is there a tester you recommend if I have questions or get error codes?

Hello @ConnorLand, are you intending to run through the guide to test it? That would be awesome to be honest. :)

[weirdwater]

First pass of my review. So far I have checked the index and part 1. I will probably get to part 2 tomorrow.

[weirdwater]

Finished my pass on Part 2

[legio-vi-ferrata]

Thanks for the review @weirdwater, a lot of nice catches! I addressed all threads. Can you do a re-review, please?

[legio-vi-ferrata]

@weirdwater, ready for re-re-review.

[weirdwater]

@legio-vi-ferrata I have "resolved" some of the threads, and provided a suggestion for the cryptic code description for the accessibility section. I also found some code snippet improvements along the way 🙈

Sorry, some of the comments were posted directly and one was stuck in concept-review...

[legio-vi-ferrata]

I guess the final review is done now. :)

[legio-vi-ferrata]

@ConnorLand, we have finished our internal review process. This one is all yours.

[ConnorLand]

@legio-vi-ferrata just a quick word about testing.

@weirdwater and I discussed it. Because the product changes for the widget generator are live, it's key to merge these docs ASAP. I've edited them for language and some formatting and will merge the PR presently.

I will do a full test of the docs myself and see if they require any tweaks to the instructions. I hope to finish that task this week. Thankfully, Arjo did some nice testing himself and the changes are almost all code-snippet improvements (thus, they don't break the doc's language/instructions).